Smart grid technology refers to ongoing improvements for the transmission and distribution of electricity from points of generation to consumers. A key component in a smart grid network is the so-called “smart-metering” network. In a typical smart-metering network, electricity (or other utility) meters located at a residency or other edifice are able to transmit the real-time meter readings through powerlines back to the power concentrators and provide valuable real-time electricity control and billing information for the electricity provider.
Due to power efficiency considerations and severe noise in powerlines, direct transmission of metering information through powerlines has limited scopes. Therefore, a typical smart metering network has a tree-like topology, including: 1) a data concentrator that serves as the root node in the tree (also called a base node, BN); 2) metering devices at terminal nodes (TNs) in the tree which send their metering readings back to the BN; and 3) switching nodes (SWs) which act as the branch nodes in the tree. The SWs relay the data traffic to the further hops for communication pairs (e.g., a TN and a BN) beyond their direct communication reach. The SWs and TNs in the network are collectively referred to herein as service nodes (SNs).
Powerline-Related Intelligent Metering Evolution (PRIME) is a European standard of smart-metering network. The PRIME standard defines lower layers of a powerline communication narrowband data transmission system for the electric power grid using Orthogonal Frequency-Division Multiplexing (OFDM) in the 42 to 90 kHz band. A PRIME network utilizes a tree-like topology as described above. In a PRIME network, the Media Access Control (MAC) function enables the BN, as well as the SWs to send out beacons periodically. The beacons also help all the SNs in the network synchronize their clocks and virtually chop the time domain into discrete time frames.
A Keep Alive (KA) procedure is used to detect whether the BN and SNs are alive. Conventional KA procedures require the BN to periodically send a KA request to every SN that is part of the network, and await a KA response from the SNs. KA frames allows the BN to detect when a SN becomes unreachable due to changes in network configuration/topology (bad link, channel conditions, load variations, SN leaving the subnetwork, etc.), or fatal errors at the SN it cannot recover from. The KA procedure is performed using timing (e.g., a particular fixed KA timeout value used) which is without regard to the number of registered SNs and their levels (depth) in the network.
FIG. 1 illustrates a powerline communications network 100 comprising a BN 110, SNs comprising as SN1-SN5, and SWs comprising SW1-SW4. Network 100 has 3 levels shown as Level 1, Level 2, and Level 3. FIG. 1 shows transmission of KA request frames by the BN 110 (ALV_B frames) for clarity to only SW1, SW2 and TN1 and the response frames from these SNs (ALV_S frames). Although the KA frames are beneficial for allowing the BN 110 to detect the connectivity of the respective SNs in the network 100, KA frames introduce additional traffic overhead in the network. It is noted that both the ALV_B and ALV_S messages are transmitted in an unicast fashion to each SN in the network 100 which further adds to network overhead.